My 40HP is running on when it's hot/at operating temp. Here are what the plugs look like. The runnin-on seemed to happen when i started using ULP (as opposed to PULP) cyclinder's #1 and #3 seem a bit lean, though #2 & #4 look pretty spot on. So there would not be any bits of carbon etc that would be 'dieseling' the engine when i turn it off. Also, when the engine does stop kicking over when i turn off the ignition, it stops with a bit of a clunk and very abruptly.




help?

What is your timing set at??

Try PULP again and see if it stops??

Do you have any idea what the compression ratio was set at??

some of these shot were taken in the shade so you can see the difference...nn[ Edited on 22-9-05 by oval TOFU ]

timing's at10 degrees BTDC..

yeh, I'll fill up with PULP next tank... no idea what the compression's at... i know it's got good compression though..

From what I've read (I'm not expert) running on can be caused by two things. One is too lean, the motor is too hot and the heat will detonate fuel after the plugs stop firing. And two, if it's too rich, the carbon buildup can heat up to the point where it will detonate fuel after the plugs have stopped firing.

Given that you are using a lower octane fuel, which causes the engine to run leaner, my guess is that it's running hot...

Like I said before, I'm no expert and am probably wrong here

I would set the timing at 7.5 BTDC and go back to premium

I am with dave on this one ...too far advanced knock it back to what dave said 7.5 and run pulp..cheers steve

Same thing happend to me when I first filled up with ULP, the octane rating was too low, I just went back to PULP and it's been OK.

cool (no pun intended) I gave my enriched mixture by 1/4 of a turn but it still ran on.. so the next tank will be PULP - sigh.. and these things are supposed to be frugal and cheap to run!

Thanks for the advices peoples! This community rocks my jocks

What does pinging sound like? A high pitched tapping noise when you apply the gas pedal? (kinda sounds like a small bolt rattling?)nn[ Edited on22-9-05 by oval TOFU ]

yes

"usually" under load.

a marble in a glass jar.
a loose exhaust system

Stand on any corner and wait till some one comes along in a Lancer or Magna (dunno why - these cars almost ALWAYS do it :jesus ) you will see them slow and then try to accelerate in top or 3rd.
THAT is the noise

Yep thats what pinging ssounds like Chris. Not good.

Optimax is the key to a sweet running Volksie motor in my humble opinion.

Now I think of it..... I've used ULP the last 2 tanks, and my carby had a spazz...?

yeh PBB, sounds like our running cost just jumped another 10c per liter!

hows ya bug btw?

Men
You need to know and understand that no amount of ignition timing changes will affect run-on or deiseling to any extent.
The bloody ignition is switched OFF. Hell, pull the plug leads and the thing will sit there clanging away!!!
Altering timing from near standard results in loss of performance or at worst detonation which further promotes the heat buildup. WOFTAM!

The engine is suffering from auto-ignition (Deiseling)and you could adjust the timing to 100 degrees BTDC but them plugs just dont spark after the key is off so forget that.

Deiseling is caused by local hot spots in the combustion chambers, often from coke left over from the combustion of oil and plenty of other factors. This coke buildup can glow red hot and ignite incoming fuel.

Enrichening the idle mixture often PROMOTES deiseling.

The best strategy is to lift the heads and decoke it and look for any sharp edges in the combustion chambers and lightly blend them out.

Another strategy worth investigating is what Ford employed in 1600 Escorts that suffered pretty badly from deiseling. They fitted a solenoid air valve that vents the inlet manifold to atmosphere (via a small filter) when the ignition is turned off.
This way, little fuel can be drawn into the engine on shutdown and the engine dies pretty much straight away.
The system is characterised by a hissing when the ignition is switched off.

Again, you can frig with your ignition timing until the cows come home but you will NOT solve your problem completely. Fueling up the idle mixture will simply exacerbate the problem. You DONT want fuel in there to be ignited.

You either live with it and kill it with the clutch or deal with the problem by decoking it or fitting a vent valve.

Good luck.

L8tr
E

L8tr
Enn[ Edited on 22/9/05 by tassupervee ]

I have also experienced running on occassionly in my Pobjoy 1380 in the '63 single cab. One of the dealers in Canberra advised to go to a higher octane unleaded and that should fix it. I still run ULP and have not changed as it does not do it too often.

Is your cutout solenoid working properly? I agree with everyone elses diagnosis of the problem though. had the problem myself. That what when I experimented with LRP.

I've changed the timing to 7.5 and I'll be running PULP again as soon as my tank gets low enough. Do I have to go for 98RON? I was previously using 95 without any probs, so logic would tell me to go back to what was working yeh?

My tinware is all saavy. I had replaced the front and rear seals and made sure the tinware is pretty tight.

I'm running a 30PICt-2 carb - I have no idea what size jet I've got - how can I tell?

95 will be fine,
And Tassupervee,The timing does make a difference, if you run your timing too far advanced, up goes you combustion chamber temps, and thats is what promotes detonation.
I know the spark plugs don't fire with the ignition off!!

Not necessarily! And Im not going to bother with an explaination. Look it up. google is your friend!
But, whatever, bottom line is the combustion chambers have hot spots causing auto-ignition and any magic carb/ignition adjustments will have precious little lasting effect other than to reduce performance and economy and there is not enough spare performance to comfortably loose in a kraut.

Either live with it or fix it properly, and forget all the bandaid wives tales.
L8tr
E

PULP fixed my the runnin on in my vw, and also made it run a bit sweeter, a bot more expensive but u have to live with that or start walkin

Well, I've chucked in PULP and retarded the timing to 7.5, and it's made a lot of difference - running on is only one or two cylinder expansions (if ya know what I mean). So I'm going to run Optimax in the next tank to really clean out the remaining crap thats causing the run-on... should probably clean my plugs a bit too..

hmmmm.......google

ok

a few things that have not been mentioned.

A high idle speed

Spark plugs the wrong temp range. eg BP6HS

Shut off solenoid not working


most sites confirmed heat as the main culprit - caused by lean fuel, low octain, timing and carbon build up.
All the sites i looked at said there would be a sufficient build up of carbon to cause hot spots if the other factors mentioned (timing etc) were present.

Food for thought

Barry

ok

My idle's fine and smooth
My spark plugs are in the correct heat range - those Bosch one - W8AC or whatever
Does a 30PICT-2 have a shut off solenoid?

If when I change my plugs and it still runs on a tiny bit - how do I get rid of the exsisting coke in the cylinders? (theoretically speaking - I'm going to run a tank of Optimax to see if that'll clean it up first)

Optimax will NOT remove carbo deposits in the combustion chambers.
As far as a stock Veedub engine is concerned, the only thing special about Optimax is the price.

There are quite a few methods of removing carbon ranging from high concentrations of Caltex Techron fuel additive to revving the engine up and pouring in water into the carb, not enough to stop the engine mind you!.

To varying degrees, some of them work, but nothing works like lifting the heads and adding elbow grease.

Its as simple as that.
L8tr
E

I agree with most of you but

I think your comp ratio is high and that is the reason why you were suppose to run PULP. If it was just the carbon, cleaning it will only help until it builds up again.
The other reason for me saying it is high comp. is because you mentioned pinging, and you described it spot on, and that together with the lower octane ULP and dieseling points to high comp. ratio.
I would say, run PULP and timing 7,5 degrees (to be on the safe side with the pinging).
You could fit a idle cut off solinoid in place of your standard idle jet, it gets power from your + terminal on your coil.

Hermann

yes your carby has a shut off solinoid.

its on the right hand side. (facing the engine) there should be a wire coming to it and the auto choke. the shut off solinoid is a short cylinder.

turn on your ignition and undo the wire from the solinoid and then touch it to the terminal a few times. u should hear a clicking sound. this means its working.

mine runs on occasionally. if its poorly tuned or if im forced to run shitty fuel. usually i run it on optimax and its fine.